@my-option: true;

div{
  & when (@my-option = true) {
    button {
      color: white;
    }
    a {
      color: blue;
    }
  }
}

// 

@usedScope: global;

.mixin() {
  @usedScope: mixin;
  .cont when (@usedScope=global) {
    background-color: red;
    color: black;
  }

  .style when (@usedScope=mixin) {
    background-color: blue;
    color: white;
  }

  
}

.mixin();